Creates earthquake spectra (horizontal and vertical) according to the International Building Code. You must also select the appropriate IBC revision from the list.
The horizontal design response spectrum is based on IBC 2000, Fig. 1615.1.4 shown below.
Ts=SD1/SDS & T0=Ts/5
The vertical spectrum is set to 20% of SDS (from 1617.1.2) across the entire period range.
IBC generally uses the same spectrum data parameters as ASCE7.